Combined steel and rubber spring



E. H PIRON COMBINED STEEL AND RUBBER SPRING Jun 29, 1943.

7 Filed April 2, 1940 2 Sheets-Sheet 1 INVENTOR. 1 Z 777 2 /12 ATTORNEY.

June 29, 1943. E.'H. PIRON i COMBINED STEEL AND RUBBER SPRING FiledApril'2, 1940' 2 Sheets-Sheet 2 1 VENTOR Zl'W/V 7 3/0 ATTORNEY PatentedJune 1943 oonmnmo s'rsnr. arm a scam and n. Piron,

Transit New York New York, N. 1.. mm Research CorporatiomacorporationolApplication April 2, 1940, Serial No. 827,477

This invention relates to vehicle springs and hsstor its primary objectto provide a spring. suitable for use on vehicles, and particularly railvehicle trucks in the springing system or which it is desired to have aload deflection ratio which i increases with increased loading,

More specifically, the main object is to-provide a combination steel andrubber spring, the

term "stee as here used being intended to generally designate coilsprings, and the term "rubberbeing intended to generally designaterubberor equivalent or substitute material. According to this object,the invention provides a steel spring, having a constant load deflectionratio, in combination with a rubber spring having a load deflectionratio which increases with the load. This results in a combined loaddeflection ratio whichlikewise increases with the load.

An important factor which must be taken into consideration in the designor rubber springs is creep; When a piece of rubber is strained, by

application of a load thereto, the deflection does -not stop when theload becomes constant, but

continues as long as the load is maintained, but at a rate decreasing intime. This characteristic, commonly called creep, is also called slip orcold flow, and is distinguished irom the elastic deflection oi therubber by the factor of time. The result of this phenomenon is that therubber does mt instantly ain itsprevious dimensions when the load isremoved. The-part oi the distortion which is elastic deflectiondisappears immedia ely. while the "creep distortion disappearsprogressively. Anotherobiect oi theinvention is to reduce the creep. andin some casesto practically eliminate it. l'bri' this p pose therfsteeland rubber springs arejsoecorrelated that the rubber springispartiallybr completely relieved.

15 Claims. (0!. m-ss) able load deflection ratio in the presence of eisting limitations and available space. In other words, the inventionmakes possible the obtaining of load deflection curves with proper loaddeflection rates under various loads which, otherwise, would bediflicult, u not impossible, to obtain with steel'sprinjgs or rubbersprings alone. In the case oiasteel spflng, interposed be-' tween asupporting member and a spring sup ported member, and providing verticalflexibility, it is necemary in general toprovide guides or articulationsbetween the supporting and supported members to prevent relativehorizontal displacement thereof. The invention has as a ll furtherobject to combine, with the steel spring,

a rubber spring which accomplishes the purpose above mentioned, and alsofor the purpose of elastically opposing iorces so directed that theywould produce horilontal displacements between 20 the mmortal and B9901!!! members. In this manner the necessity for guides orarticulations between the supported and suppor i mem s I ismadeunnecessary. Y Other objects and advantages will become more fullyapparent reference is had to the accompanying drawings wherein myinvention is illustrated, and in which:

Pig. is a plan view illustrating a fragment of struck irame combinedrubber and steel springing unit.

a 2-2 oi Pig. 1,

supported irom an. axle housing u vol-um section. taken on the use ofstresses when the vehicle is emptied oi its spring, thus reducing theservice stresses oi the 4 spring assemblyin was with two axles.

' j ashait, oi metal or. its equivalent, having its upper end] securedto an element 2 which represents, for

commercialloading,theloadbeingthenpartially or entirely supported by thesteel spring.

Another object isto provide a combination teel and ub sp i in which t emilder po'r- J example, a frame member or a rail vehicle truck, tion orthe service load is imposed upon the steel- 48 and which is hereinaiterreferred to as the supported member. "lhelowerend' oi the shaft Iextends loosely through a cylinder' I mounted on an-element l, whichrepresents an axle housing on a rail vehicle truck. Another cylinder 6so is mounted on the axle housing on the other side and is s'imilartocylinder I. Both cylinders 3 and I are hereinaiter referred to as loadsupporting the fo at on of a omposi e sp e p oyin members. The cylinder3 contains ,a rubber a combination oi steel and rubber springs in aspring and the cy inder [contains a steel spring. manner making it mucheasier to obtain a-valuls l The rubberspring employed is of a typehaving rubber spring, and increasing its useful life. In the, case oistreet car trucks limitations of design and available space, etc., makediiiicult the provision of a spring having the desired load deflectionratio under allconditions of loading. This invention has ior anotherobject to teach inner surface of the cylinder 3. Beneath the a mass 1the cylinder 3 is formed with a flange 8, and secured to the shait iabove the mass is a load imposing member 9 having one or more steps.

The upper surface of the mass is formed with or more steps l0,corresponding in number "to the number of steps on the member 9, whichare originally of frusto-conical form and separated by frusto-conicalrisers. The spring is shown in a loaded condition to illustrate themanner in which the steps of the elastic plastic mass are progressivelyengaged by the stepped member 8..

In the position shown, the uppermost step Ill and its riser portion arestill unseated and may be taken to represent the shape of the othersteps 10 prior to deflection thereof.

As is shown and explained in detail in my Patout No. 2,245,295, thestepped member 9 and the steps ID are so correlated that they functionto limit distortion of the elastic material in different regionssuccessively, as a result of application of a load thereto. That is, asone region is subjected to a safe load the lowermost step I.

seats against the lowermost step on the stepped member 9, and thisregion becomes stabilized against further distortion. Followingstabilization of the first region, an added load causes stabilization ofa second region, and the remaining steps function in like manner. Theresult is that the typical load deflection curve of this spring may bealtered to obtain softness under light loads and increasing stiffnessunder increasing loads, or, in other words, a load deflection ratiowhich increases with the load."

A steel coiled spring H is mounted in the cylinder 6, and is compressedbetween a flange ii on the lower end of the cylinder 6 and a spring seatmember i3 secured to the supported member 2.

tially constant. As shown in Fig. 4, the steel spring has a constantload deflection-ratio, and the rubber spring has a load deflection ratiowhich increases in value with the load. The springs, as is hereinafterexplained more in detail, are so arranged that the rubber springs begintoact after the steel springs have been com-. pressed a predeterminedamount. The combined curve, starting at zero, increases at a constantrate until the rubber spring begins to act, and from that point thecurve increases at a rate dif- Serent from the rate of either spring.

In obtaining the desired distribution of the load between the twosprings, means must be provided for maintaining the member 2'substantially parallel to the flanges 8 and I2 of the load supportingmembers 3 and 6. In rail trucks this condition may be realized by theaction of the assembly at the other axle, or by placing one kind ofspring, the steel spring for instance in front ofthe axle 3 at one endthereof and in the rear at the other end. This is more particularly exvplained later.

An example of the ratios found satisfactory for street car use isillustrated in the chart of Fig. 4. The steel spring has a constant loaddeflection ratio of 666 lbs. per inch and the rubber spring has thefollowing reactions:

vIn some installations it is desirable to provide a unitary assembly ofthe steel and rubber springs, as illustrated in Fig. 3. In this case arubber spring in is mounted in a cylinder 30. and coacts with a steppedmember So on a shaft la which is secured to the supported element 2a.

The cylinder So has an outwardly extending flange l4, and a steel coiledspring lid is compressed between the flange ll and a springseat memberI3a attached to the member 2a.

It is evident that, in both forms described above, both springs are sorelated that their main deflections are in a direction axial withrespect to the shaft I, or la. The rubber spring also acts toresiliently oppose relative movement of the shafts and cylinders indirections radial with re-- spect to the shafts.

Vehicle springs having a constant load deflection ratio result in ariding quality which is relatively hard under light loads and becomesincreasingly softer under heavier loads. It is desirable, of course, tomaintain the riding quality substantially constant, regardless of theload carried, and the present springs are so designed that the ridingquality is maintained substan Deflection 1 inch, reaction 700 lbs.Deflection-2 inches, reaction 2000 lbs. Deflection 3 inches, reaction4000 lbs.

The springs are so arranged that the rubber spring starts to functionwhen the steel spring is deflected 3 inches, and the total reactions areas follows:

Deflection Reaction Steel Rubber Steel Rubber Total Inches Inches Poundslounds Found:

It will be seen from the foregoing that, with the spring assembly heredisclosed, it is possible to correlate a rubber spring, having a loaddeflection rate increasing with the load, so that its use in combinationwith a spring having a constant load deflection ratio it gives aloaddeflection curve with a load deflection rate increasing in apredetermined manner with the load.

With a load distribution such as above described, wherein the steelspring is initially col pressed, there is a tendency for the member 2 tobecome displaced from its normal parallel relationship with the flanges8 and I! of the load supporting members 3 and G. This is be- I cause thereaction of the steel spring is initially greater than the reaction ofthe rubber spring, and if asingle unit such as shown in Fig. 2 isconsidered in the absence of any other truck structure, the steel springwould act to compress the rubber spring. However, it is pointed out thatthis would defeat the purpose of the invention, and it is contemplatedthat such an action be prevented in the final truck assembly.

As shown in Fig. 5, at one end of the axle housing s steel spring H ismounted in front and a rubber spring I is mounted behind. At the otherend of the axle housing the order is reversed, and a rubber spring I ismounted in front and a steel spring ii is mounted behind the axlehousrangementof the-moose sembly at one endof the frame memberscountertheassembly at the other end, and the arby the matteroffconvenience inassembly, 1

In applying a load upon a springanit, the

steel and rubber springs may be, sald'to act in parallel, in the respeetthat'the eflects of loading are divided and distributed through bothsprings, and also in the respectthat in rlg. 2 the springs are arrangedinparallel or side by side relation on opposite .sidesof the axlehousing so that they share the load Jointly. Boweventh'e steel spring iscompressed a predetermined amount before any load is applied to therubber spring, and in this respect it might be stated that the'twosprings act in serieslto the exte'ntthat springs are so correlated thatthey both function 1 to support the normal static light load, which willbe the weight of the empty car body and the means whichsupports it onthe frame members. Therefore, when the springs are in use, both functionjointly in the support of the load. Whatisclaimedisz,

. w n s Oandif suchas Fig. 6, the asv aaaasrs I,

' mined amount prior to any deflection ands supported said slementsbeingby' a springing element composed of amass of elastic plastic materialhaving cylindrical inside and outside surfaces contacting the outsidesnd in-' side surfaces respe'ctivelyof said cylindrical elements, saidgenerally conical top and bottom surfaces, ,ione or the latter surfaceshaving steps them-deflection limiting means on one of said elementsforcoaction with said steps,

and a second spring interposed between the supporting and supportedmembers to. act Jointly with theflrst named springing element, saidsecond springhaving a constant load deflection ratio and said secondspring being so arranged that in the presence of loading it deflectsa'predeterof the-elastic plastic springing element.

5. In combination, an axle housing, a drical" member arranged on eachside of said,

housing, a frame member, a shaft depending from said frame member'andextending loosely through I f'one cylindrical member, a coiled springinthe one deflects flrst. As explainedabove, the two 1. A compositespring assembly adapted port a supported member on a supporting member,comprising a metal spring having a constant deflection ratio. arubber-spring, means for varying the load deflection, rate of saidrubber spring to provide a load deflection rate which increases withtheload according to a selected curve, and means for the spring assem-vbly betweenthe'and supporting memfor joint such manner that when'a loadis initially; applied the metal spring isdeflected a predeterminedamount "deflectionof theruhber spring. 5 1, In combination, supportingmember, a

j supported member, a spring between said members, said, compositespring comprising a spring having a constant load'deflection ratio. .anda springing element composed of a mass. of .Felastic plastic materialhavingfconcentric' cylininner and outer surfaces securedto parts oflthesupporting and supported members, said having generally conical. topbottom surfaces, one of said conical "surfaceshaving-at least ones'tep'thereon, and; on limiting means coacting with saidste'p; i

, -3. A composite spring; comprising ,ccnce ntric 3 cylindrical elementsconnected to a supporting member and a supported-member respectively, 7,said cylindrical elements being separated by a springing elementcomposed of a mass of elastic prior to any 'therethrough, and said massother cylindrical member and engaging. said frame member, 'aplasticelastic'mass in the cylindrical member traversed by the shaft, said masshaving ,its outer surface contacting the inner surface of itscylindrical member and its in ner surface contacting the shaft whichextends drical member arranged on each side of said' housing, a framemember, a shaft depending from said frame member and extending looselythrough one cylindrical member, a coiled'spring in the other cylindricalmember and engaging said frame-member, an elastic plastic mass in theflrst cylindrical member, said mass having its outer surface contactingthe inner surface of said flrst cylindricaljmember and its inner surfacecontacting the shaft which extends therethrough, and said mass havinggenerally conical top and bottom surfacea-sa'id coiled spring being soarranged that in the presence of loading it deflects a predeterminedamount prior to any deflection of the elastic mass.

plastic material having cylindrical inside and outside surfacescontacting the outside and insidesurfaces respectively of saidcylindrical elements. said mass having generally conical top and bottomsurfaces, one of the latter surfaces having stepstherein,deflection-limiting means on one of said elements for coaction with saidsteps, and a second spring interposed between the supporting andsupported members to act jointly with the flrst' named springingelement, said secspring h-aving a constant load deflection ratio.

4. A composite spring comprising concentric cylindrical elements to asupporting 8. In combination, an axle housing, a cylindrical memberarrangedon each side of said housing, a frame member, a shaft dependingfrom said frame member and extending loosely through re-- it Incombination, an axle housing, stylindrical member arranged on each sideof said housing, a frame member, aj-shaft depending from saidframemember andextendingloosely through one cylindrical member, a coiledspring in the other cylindrical member and engaging said frame member,an elastic plastic-mass in the 7 first cylindrical member, said masshaving its outer surface contacting the inner surface of its cylindricalmember and its inner surface contacting the shaft which extendsvtherethrough, and said mass having generally conical top and bottomsurfaces. one of said latter surfaces having steps therein, anddeflection limiting means coacting with said steps.

spective cylindrical member, a coiled spring in the other cylindricalmember and engaging said frame member, a plasticelastic mass in thefirst cylindrical member, said mass having its outer surface contactingthe inn r surface of the first cylindrical member and its er surfacecontacting the shaft ,yvhlch extends therethrou'gh,.and.

said mass having generally conical top and bottom surfaces,'one of saidlatter surfaces having steps therein, and deflection limiting meanscoacting with said steps, said coiled spring being so arranged that inthe presence of loading it deflects a predetermined amount prior to anydeflection of the elastic mass. i. v

, 9. Inicombination, concentric cylindrical load im'posingand loadreceiving members separated I by aspringing element composed of a massof elastic plastic material having cylindrical inside andoutside-surfacescontacting the outside andinside surfacesrespectively ofsaid load imposby a springing element composed'of a mass of elasticplastic material having cylindrical inside and outside surfacescontacting the outside and inside surfaces respectively of said loadimposing and load receiving members, said mass having generally'conicaltop and bottom surfaces, at least one of said latter surfaces havingsteps therein, deflection limiting means on one of said members forcoaction with said Steps, and a metal coil spring interposed betweensaid load imposing and receiving members in substantially concentricarrangement with the cylindricalload imposing and load receivingmembers. I

11. In combination,- concentric cylindrical load imposing andloadreceiving members separated by a springing element composed of a mass ofelastic plastic material having cylindrical inside and outside surfacescontacting the outside and concentric arrangement with the cylindricalload imposing and load receiving members, said coiled spring being soarranged that in the presence of ing members haying springstherebetween, one oi.-

loading it deflects a predetermined amount prior v elastic plasticmaterial having cylindrical inside and outside surfaces contacting theoutside and inside surfaces respectively of said load imposing and loadreceiving members, said mass having generallyconical top and bottomsurfaces, at

least one of said latter surfaces having steps therein, deflectionlimiting means on one of said members for coaction with said steps,and'a metal coil spring interposed between said load imposing andreceiving members in substantially concentric arrangement with thecylindrical load imposing and load receiving members, said coiled springbeing so arranged that in the presence of loading it deflects apredetermined amount prior to any deflection of the elastic mass.

13. In combination in a vehicle springing system, load transmittingmembers and load receiving members having springs therebetween, oneofsaid springs being .of the constant load deflection ratio type, theother of said springs being of rubber-like material, and means carriedby one of said members imposing loading on an area of said other springwhich increases with increasing vertical load.

14. In combination in a vehicle springing system, load transmittingmembers and load receivsaid springs being of the constant loaddeflection ratio type, the other of said springs being of rubber-likematerial, means carried by one of said members imposing loading on anarea of said other spring which increases with increasing vertical load,and means carried by one of said members extending through saidrubber-like spring for transmitting all relative horizontal movementsbetween said members thereto.

15. In combination in a vehicle springing sys-- tern, load transmittingmembers and load receiving members having springs therebetween, one ofsaid springs being of the coiled steel type and adapted to deflectaccording to a constant load deflection ratio, the other of said springsbeing of a rubber-likematerial and being adapted to deflect undervertical loading by a combination of shear and bending stresses, andmeans carried by one of said members for contacting an area of saidother spring which increases with increasing vertical deflection wherebythe proportion of shear to bending stresses progressively changes.

' EMIL H. PIRON.

